如何在断网状态下播放缓存音频？

function loadAudio(url) {
  fetch(url)
    .then(response => response.blob())
    .then(blob => {
      let reader = new FileReader();
      reader.onloadend = function () {
        let base64data = reader.result;
        localStorage.setItem('audio-cache', base64data);
      };
      reader.readAsDataURL(blob);
    });
}

function playCachedAudio() {
  let base64data = localStorage.getItem('audio-cache');
  let [contentType, base64String] = base64data.split(';base64,');
  let decodedData = atob(base64String);
  let arrayBuffer = new ArrayBuffer(decodedData.length);
  let uint8Array = new Uint8Array(arrayBuffer);
  for (let i = 0; i < decodedData.length; i++) {
    uint8Array[i] = decodedData.charCodeAt(i);
  }
  let restoredBlob = new Blob([uint8Array], { type: contentType });
  let audioElement = new Audio(URL.createObjectURL(restoredBlob));
  audioElement.play();
}